Optometry case study: Normal-tension glaucoma

History

Px: 82-year-old Caucasian femaleReason for visit: Noticed her RE wasn’t as clear as her LE, even with optical correction from a year agoGH: Controlled hypertensive and migraine suffererMeds: Multiple, but no steroidal medicationPOH: Bilateral pseudophakia for the last 6 years. Was initially diagnosed at the time with glaucoma by the ophthalmologist but was lost to follow upFOH: No history of glaucoma

Repeatable paracentral visual field defect in the RE in the superior nasal quadrant – this correlates to the inferior temporal thinning of the ganglion cell layer (Figures 4 and 5)

Figure 4. Visual field from a year ago showing a paracentral defect in the RE

Figure 5. Visual field from most recent presentation showing a repeatable paracentral defect in the RE

Amsler grid:

Absolute scotoma superonasal to fixation in the RE. LE normal

Diagnosis & Management

Differential diagnosis:

Normal-tension glaucoma

Secondary open-angle glaucoma

Angle-closure glaucoma

Physiological disc asymmetry

Optic atrophy

Diagnosis: Normal-tension glaucoma

Management:

Patient was advised that the RE’s central vision wasn’t as good due to the absolute scotoma caused by loss of ganglion cells from glaucoma.

Patient was referred to a local glaucoma specialist for management as well as to Glaucoma Australia to help facilitate understanding and encourage compliance with treatment and reviews.

She was also advised to encourage her family members to get their eyes checked.

Discussion

Normal-tension glaucoma (NTG) is a form of primary open-angle glaucoma in which IOP is less than 21mmHg and is one of the most common forms of glaucoma in Australia, Japan, Western Europe and the US1-2. Compared to other forms of glaucoma, NTG has a relatively slower average rate of progression with reported mean deviation visual field loss of 0.36dB-0.41dB / year as opposed to 3.13dB / year in pseudoexfoliative glaucoma and 1.31dB / year in hypertensive glaucoma3-4. However, NTG visual field defects tend to be more localised, dense and closer to fixation5-8. In this patient’s case, it has affected her central vision in the RE, and she is now symptomatic.

Risk factors for progression of VF defects include female gender, migraines and disc haemorrhages9. Disc haemorrhages are also very characteristic of NTG as well as inferotemporal rim thinning and notching10.

Since ophthalmological assessment, the patient’s IOP has been controlled with prostaglandin analogue eyedrops (Xalatan, latanoprost 0.005%) and she is being reviewed on a six-monthly basis.

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